Non-contact joining or welding of plastic materials is well-known. In a typical system, two or more webs or films are conveyed over a platen and a focused laser beam is used to heat the web material to a temperature sufficient to join the multiple layers. In some cases, the weld or joint is continuous along the travel path of the web(s), such as for an edge seam. Welds or joints that are not collinear with the travel path of the web(s) require different considerations. For instance, transverse welds are usually formed by scanning the laser beam transversely across the webs at or immediately adjacent nip rollers used to hold the webs together.
The prior techniques for forming collinear and transverse welds, or for that matter welds that follow a more complex pattern, generally permit limited throughput. Moreover, the prior techniques are relatively inflexible, requiring significant changes to the process and equipment to generate different weld patterns. There is a need for a non-contact method for welding web fed materials in which the welds may be provided in a variety of patterns across a finished product. Particular examples of finished products include multi-pocket sheets such as used in photo albums, business card organizers, cd carriers, protective pages and the like.
One example of a product P is shown in FIG. 1. The product is formed by two or more webs or sheets of a film, such as a polypropylene or polyethylene film. The product P may include several cut-outs or cuts C to provide certain functional elements, such as pockets or mounting holes. The multiple sheets are joined or welded at several seams S which form the periphery of the product as well as the periphery of certain features of the product, such as pockets for holding pictures, cards, discs or the like. In the illustrated product, six uniformly sized pockets are provided. However, in other products, more pockets may be provided or pockets of different sizes and shapes may be included. It can be appreciated that the various product configurations can add complexity to the seams S that must be formed.